Johnstown, Colorado 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

635
FXUS65 KBOU 262109
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
309 PM MDT Thu Jun 26 2025

.KEY MESSAGES...

- Hot Friday and Saturday with isolated afternoon storms.

- Cooler Sunday and Monday with higher coverage of storms and a
  threat for some of these storms to be strong to severe.

&&

.DISCUSSION /Through Thursday/...
Issued at 220 PM MDT Thu Jun 26 2025

Water vapor satellite shows dry air over Colorado with southwest
flow aloft. There is some weak subsidence that is limiting
convection this afternoon. However, a few stray storms are forming
over the Palmer Divide and east to northern Lincoln County. High
resolution models are also starting to come into better agreement
that showers will form over the foothills late this afternoon and
into the evening and these showers will move over the I-25
corridor this evening. Brief moderate rain with gusty winds will
be possible with these showers. PoPs were increased to get a
mention of showers in the forecast this evening.

Temperatures aloft will increase on Friday as light zonal flow
aloft will be in place. This will allow high temperatures to the
reach the low 90s across the I-25 corridor and plains. Model
guidance also suggests a weak low level convergent boundary will
form generally from Deer Trail to Julesburg. Isolated storms will
form along this boundary by the late afternoon. Soundings show a
large boundary layer up to around 600 mb with dry adiabatic lapse
rates. This suggests strong wind gusts up to 60 mph will be
possible with the strongest storms especially north and east of
Akron. Elsewhere, a few light showers and weak storms could form
over the higher terrain and move onto the adjacent plains.

Saturday will be very similar to Friday as hot temperatures and
isolated storms will again be possible. Gusty winds will be the
main threat from these storms.

A cold front seems likely to move through the northeast plains on
Sunday bringing northeast winds. The majority of guidance
indicates dew points may be in the 60s and upper 50s behind this
front. Given the upslope winds and moderate instability, it is
expected that storm coverage will increase with 30-40% coverage.
An upper level jet will pass to the north of Colorado on Sunday
and may help to increase the deep layer shear close to the WY/CO
and NE/CO borders. Some storms may be strong to severe in far
northern Colorado with large hail and damaging wind gusts the
primary threat.

Monday will have east-southeast winds across the plains with
healthy dew points. Moderate instability will be under a strong
cap due to a ridge and warm temperatures aloft. The upslope flow
may help to generate storms in the foothills but it is uncertain
if the storms will be able to survive on the plains. Monday will
be the coolest day of the 7 day forecast.

A ridge aloft will strengthen on Tuesday and Wednesday and highs
will increase to normal. Isolated storms will likely develop over
the higher terrain each day.

&&

.AVIATION /18Z TAFS through 18Z Friday/...
Issued at 1158 AM MDT Thu Jun 26 2025

VFR conditions expected through the TAF period. Light winds
today expected to increase out of the southeast in the late
afternoon. Recent high resolution model runs have been more
consistent in showing showers over the terminals this evening.
While these are unlikely to impact the terminals, it is possible
that wind gusts up to 25 knots occur. There will be normal
drainage flow tonight and light winds Friday morning. In the
afternoon on Friday, storms to the southeast of Denver will likely
push an outflow boundary through that has moderate southeast
winds with gusts up to 30 knots.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Danielson
AVIATION...Danielson